The six included four Russians, a German and a Frenchman who entered the facility March 31 in order to see how their bodies and minds would cope with the isolation and limited communication from Earth. Two of the six are astronauts, the others are an oncologist, a sports physiologist, an airline pilot and an army engineer.

By all accounts, the experiment went well, although concrete results from the 72 tests conducted during the 105 days won't be released for several weeks. The men appeared to be in good health as they stood together in a row in front of a large assembly of journalists and staff after exiting to loud applause.

'Giant Leap for International Mars Exploration'

"It was a small step for mankind and a giant leap for international Mars exploration," Johann-Dietrich Woerner, chairman of the German Aerospace Center, said during a news conference after the crew's exit from the module.

The experiment is part of a larger project dubbed "Mars 500." The three months the men spent in isolation are a precursor to another simulation to take place in 2010, when another crew will submit themselves to 520 days in isolation, the projected time it would take for a return trip to Mars.

In almost a year and a half, the experiment will attempt to mimic the 250 days it will take to get to Mars, a 30-day stay, and the 240-day return while the crew adheres to a strict schedule and diet.

The six-member crew lived in a cramped 19,500-cubic-foot facility where they were put through various scenarios that they would face, including a simulated landing on Mars, a 20-minute delay in communications each way with Earth and various emergencies.

Skeptics Criticize Isolation Experiment

Skeptics have criticized the experiment because, in the backs of their minds, the crew members knew that they could exit the capsule if they had to, unlike if they were millions of miles away from Earth. The experiment also didn't simulate some of space's basic elements like weightlessness.

"I must admit that I have absolutely lost the feeling for time on a long-term basis," German Oliver Knickel wrote in a diary entry posted on the European Space Agency Web site (which is working on the project with the Institute for Biomedical Problems). "I, absolutely, have no idea about the total length of time we have spent inside the module now."

After a quick medical, the team members arrived at the news conference and told reporters one of the reasons the experiment was successful was because they had become a very close-knit group.

"We all had some personal competence to detect in others how far we could push them," said Frenchman Cyrille Fournier, calling the group dynamic respectful and polite. "We avoided really critical tensions."

The friendship theme was repeated by each member of the team, a crucial factor in helping them maintain some sense of normalcy while cut off from the outside world.

Cosmonaut: Political Will Lacking for Mars Mission

"You were working all the time," Russian Alexey Baranov said. "Even when you were resting, you were far from family and friends. It was difficult to prepare, psychologically, for that."

There are no official plans yet to go to Mars. The Russian space industry is ready to start working on a mission but the political will is missing, said Yuri Karash of the Russian Academy of Cosmonautics. He hopes a mission will happen not just for space exploration, but for the practical uses on Earth that will result as they did from the initial Apollo missions to the moon.

"We learned a lot about human biology, physiology," Karash said of the Apollo program. "Imagine how much they will learn [from going to Mars] about resistance of the human body to unfavorable conditions of the long-term human space flight. This knowledge can be applied to Earth."

Is Mars 'the Next Step'?

The notion that Mars is "the next step" arose from many participating in the event, and the consensus is that it will only be feasible if countries and space agencies band together, as they have with Mars 500. Karash hopes it will happen in the next 15 years, but the European Space Agency and NASA are planning for closer to 30 years out.

"It's important for humankind, it's no longer just a national priority, it's an international priority," said Igor Savelev of the American National Space Biomedical Research institute. "Any large project like flight to Mars will have to be international."